Well, there are currently 2 really good save editors out:code.google.com/p/gnomeextractor/The gnome extractor edits the gnome's skills and abilities (and pre-set professions).forums.gnomoria.com/index.php?topic=1140.0Save-game editor does a lot more with the terrain (such as expanding the ores, water editing, modifying animal types, tree types, etc etc)

From what i've seen, the 'food and drink' are actual instances that are simply counted, so in order to edit the quantity, you'd have to increase what you have... (unless you were to find the location of a storage bin/block and keep the number of food in a stack at max, but i haven't looked into it (its a sandbox game, that, in my games, i always have too much food/drink)